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No available data on the 727-200C
For a group project in college, it was required to find the data of some randomly asigned aircraft. My group received the Boeing 727-200C, of which only one was produced. Due to this, no one in my group can find any data on this aircraft, only on the 727-200 Basic or Advanced types.
Mainly we have to look for dimensions, weight, in flight performance (cruising altitude and speed, endurance and range), take off and landing distances and which engine it used.
Where should I look for data? If anyone has this data available, could you share it?

You might want to check here: https://www.planemapper.com/aircrafts/C-GXFA
Apparently it was supposed to be a USAF version of the 727 but may not have been approved, and ended up in service in Canada. Here is a picture of it: https://commons.wikimedia.org/wiki/File:First_Air_727-200C_C-GXFA.jpg

So far as the FAA is concerned there is no 727-200C at least not that ever carried a type certificate. The 727 series has a common type cert which you can find here and it has no listing of a 727-200C type. There are however 727-100C and a 727C types listed and some other numberings that use the C nomenclature but none that use -200C. The image that @JuanJimenez links from wikipedia is incorrectly labeled. You can see it carries Canadian registration C-GXFA which is a 727-233 you can find more pictures of it here. Also note that the wikipedia section states only one was built and provides no citation at that.
Interestingly the Smithsonian has a model of one...


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What material is used to make the interior sidewalls panels, ceiling as well as luggage bins in a commercial aircraft?
What material is use to make the interior sidewalls panels, ceiling as well as luggage bins? All these elements seems to be made of similar material.
What is the weight these cabin interior elements represent for a typical single aisle aircraft like the A320?

I presume Polycarbonat or even more likely Fibre-reinforced plastic? I miss Polycarbonat on modern smartphones, better feeling in the hands and doesn‘t break like glass.

The materials used in aircraft are similar regardless of airline or type of aircraft, since all passenger-carrying craft must meet  flammability requirements.
The side panels, the ceiling and the luggage bins are made out of a Glass Fiber Reinforced Plastic (GFRP) that must meet fire/smoke/toxicity (FST) requirements.The small window shade panels that slide down to cover airline windows, are typically thermoformed polyetherketoneketone (PEKK) plastic sheet. Some other high performance thermoplastics can be found on an airliner's interior, like the polyetheretherketone (PEEK) and the polyvinyl fluoride (PVF) (mostly as decorative surfaces laminate).
Reference: https://www.compositesworld.com/articles/advanced-materials-for-aircraft-interiors

I'm not doubting you, however some references would turn a nice answer into a really good one.

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Why does this aircraft land nose first?
I've seen almost every aircraft land back gear first to evenly distribute the landing load between more struts.
However, I recently saw this video of a NASA Super Guppy Nose-Wheel land gear first at Mansfield-Lahm Regional Airport:

.
I couldn't think of any reason a pilot would want to do this so is there any reason as to why they would want to land nose first opposed to the conventional way that I don't know of?

You are assuming that it was on purpose.

I‘m with Michael. And maybe the angle in which the video has been shoot is deceiving. Could it be, that all wheels nearly touched at the same time?

That's pretty much how landings turn out on Super Guppy. The aim is to make a three point landing (main and nose wheels touch down simultaneously), but the Super Guppy is a tricky plane to land. Earlier versions were tricky on takeoff too: during takeoff roll their main gear tended to lift off before the nose wheel, this, ofcourse is far from optimal...
This article will give you a nice briefing on this beautifully weird plane (see page three for stuff about landing).
The ones still flying are fitted with Boeing 707 nose gear, which is shorter, sturdier and placed further behing than the original one. Despite this modification, the aerodynamics of the plane are such that it just wants to plant the nose wheel down first. Searching "Super Guppy landing" on Youtube will yield allmost only nosewheel landings.

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Non-Towered Airport Operation Logs
Do general aviation non-towered airports have to submit any types of logs to the FAA regarding total number of take-offs and landings in a given year?
I'm trying to figure out how busy a small airstrip near a property might be, I'm not having any luck getting the airstrip owner on the phone.
Thank you!

Which airport are you looking at?

Look up the airport at http://www.airnav.com/airports
It'll show info such as:
Airport Operational Statistics
Aircraft based on the field:        66
Single engine airplanes:        65
Multi engine airplanes:     1
Aircraft oper  ations:  avg 70/day *
52%     transient general aviation
48%     local general aviation

for 12-month period ending 07 April 2015

Airnav and other sites have usage data on all US airports, including non-towered ones, so someone is collecting and reporting this information somewhere.
I've read (can't remember where) that one should always use one's tail number at least once on CTAF so the airport doesn't miss out on their fair share of FAA subsidy funds, which is probably connected.  My best guess is the airport owners (or at least some of them) are recording CTAF to count tail numbers for when they have to submit their official usage data.

Of course, there are often a lot of no-radio operations at such airports as well.

@FredLarson Good point; such traffic may not be reported if there's no other counting mechanism, such as someone (or a video camera) watching the runway.

Officially there is no regulation about this and I have never encountered anything official on it in practice.
However some airports both towered and un-towered are required to collect a small landing fee typically imposed by the local municipality, of which there may be a record of. You may need to go to the local municipality or controlling authority to get the info.
You can get an idea from here as well but keep in mind this is only IFR/Flight Following/"in the system" flights.

This answer is for US only, since the question is tagged FAA
I don't know how the information is collected, but if you google "air operations xxx" where xxx is the FAA identifier for your airport, you'll find a bunch of sites that report this information.
For example, go to https://www.fltplan.com, select "Airport/FBO info", find your airport, scroll down to the tabbed section above the runway info and select 'aircraft data'.
AOPA has similar info: go to https://www.aopa.org/destinations/, find your airport, then look for the section "Aircraft & Activity".
https://skyvector.com also has this - click on the Airports button at the top left, find your airport, then look for "Operational Statistics".

If it is non-towered it is highly unlikely that such records exist since this sort of data would typically be gathered by ATC personnel.  I would recommend networking with some local pilots to get a subjective measure of its use.


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What is the relative safety record of the Sukhoi Superjet 100?
After the last crash, numerous articles state that the Superjet has a poor safety record. Two fatal crashes in 8 years is not a lot, but then again, only around 150 planes have been delivered. Does anybody have numbers of fatal crashes pr. million flights, or similar?
Accidents pr. million flights for other major airplane models: http://www.airsafe.com/events/models/rate_mod.htm

Most of the articles I have read concentrate on the poor reliability record and issues with maintenance. Did you have any specific articles in mind?

Maybe the titles are inaccurate to clickbait, but I think of articles like this:
"Industry observers:  Sukhoi Superjet Crash No Surprise": https://freebeacon.com/national-security/industry-observers-sukhoi-superjet-crash-no-surprise/
"Sukhoi Superjet 100: Plagued by serious incidents and accidents: (In Norwegian): https://www.hangar.no/sukhoi-superjet-100-forfulgt-av-alvorlige-hendelser-og-ulykker/

It doesn't matter how well engineered a plane might be, what matters is maintenance. If you cut corners or do a shoddy job, problems are bound to creep up. As the smartest mechanic I know always says, "I never replaced an engine on a vehicle where the proper maintenance was performed."

@gwally The issue is, like anything involving humans, maintenance mistakes do occur and it is simply impossible to guarantee they will not. Proper engineering allows for this by expecting that failures will occur and limiting their impact. Likewise maintenance is there to catch design and manufacturing errors. All part of the swiss cheese model.

The plane was flown into the ground with a clearly visible and well-known landing error, pitching down after a bounce. That said, to blame it squarely on the pilots is premature, especially as the crew will soon be able to shed light on what happened. I've done some of the same in simulators with heavy instrument failures, although their poor/lacking damage models let you get away with it.
On the actual question, the Superjet does not yet have a meaningful safety record of any kind, good or bad. It's seen far too little use, and it only had two accidents, one of which was confirmed as a pure human error CFIT. Driving a perfectly intact plane into a mountainside is akin to driving a car off a bridge.
This leaves one accident where the plane had any faults at all, and such a small sample size is not enough to build any sort of statistics out of.
It's also difficult to distinguish cause and effect in the plane's simultaneous loss of popularity and reduction in support service levels amidst a political rift between its manufacturer's home country and most of the world, or infer anything technical from that.

Does anybody have numbers of fatal crashes pr. million flights, or similar?

Not that I can find.
Too little data?
In terms of airline passenger miles, the SSJ100 seems to account for a tiny proportion of passenger miles in Russia.
Non russian airlines have eliminated or scaled-back use of the SSJ100
According to Time

Mexico’s Interjet said Sunday it operated five of the planes “under the highest safety standards.”
Interjet has previously said it has 22 Superjets but referred in a recent earnings report to the “gradual phase out of the fleet of SSJ100.” The company reported it lost sales after some planes were temporarily out of service after a warning from Russia’s aviation authority about a potential defect in the tail section in December 2016. Interjet also said it was seeking contractual recovery of maintenance costs associated with the plane.

Irish operator CityJet have dropped their leased SSJ100s from their fleet.
The safety issue is probably operator and environment, not planes
The reports I have read suggest that the safety issues are with the operators, regulators and airspace management.
The SSJ100 is now almost exclusively operated by Russian Airlines and Russia's air safety record is allegedly the worst in the world.
The Washington Post reports

“In Russia, there is reliably one big crash with corpses per year,” Mikhail Barabanov, an analyst at the Center for the Analysis of Strategies and Technologies, a Moscow think tank, said in a Facebook post. “According to statistics from international organizations, air traffic safety in the Russian Federation and the CIS in 2018 was the worst in the world — worse than Africa.”

You mentioned that you know about the major parts availability issues with this plane. That is a concern in itself because it may lead to safety issues. It causes aircraft to operate with many deferred items for long periods of time, and brings the temptation overlook faults and reuse unairworthy components. For this reason, FAA requires airlines have adequate spares on hand before introducing a new type and during regular operation. Similar issues occur with old aircraft, see Allegiant and the MD-80.

I agree that there is too little data at this time to compare statistics in a meaningful manner. I found some quotes on the number of flights on WIkipedia, approximately around 300.000 flights by September 2018. That would make the Superjet seem even worse than the 737 MAX, but with (thankfully!) just 2 accidents, it's hard to calculate statistics. https://en.wikipedia.org/wiki/Sukhoi_Superjet_100#Operational_history


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How do I get an FAA okay for a private runway?
The county I'd like to put a private runway (for my use only) in doesn't require any special permits because the property is zoned Agricultural, BUT they do require some form of acknowledgement from the FAA that the FAA doesn't have a problem with it being in that location.  How do I go about getting something like that from the FAA?  Who do I contact?

You're probably already aware that the FAA itself does not require the operator of a private airfield to receive any kind of approval from the FAA. However, there is a process in place to register a private airfield, and indeed the notice (not approval) is mandatory. The result of that process might satisfy your local authority.
The three FAQs starting here are pertinent. You need to file FAA Form 7480-1, either by mail or via the OE / AAA system.

Thanks for the information.  I knew the FAA itself didn't require that I get their approval for a private airfield, but was wondering what I could get from them to satisfy the County Zoning.  I will check on seek to register my airstrip.  Thanks again.

You never know when having your airstrip registered might come in handy


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Did factors specifically related to the concorde design influence the Air france flight 4590 crash?
This youtube video partially attributes the retirement of all concorde fleets to the airfrance flight 4590 crash:

Were the factors in this accident due to the concorde's design? Specifically, the tires of the concorde?

Flight 4590 hit debris on the runway causing the puncture and subsequent fuel tank rupture, fire, and crash. I'm not sure how you can say that the design isn't a factor, but it wasn't retired because of that crash alone. It flew for 3 more years after the crash, Airbus was winding down maintenance and people weren't flying as much post 9/11.

In short: No, the crash of 4590 could happen to other aircraft in the same situation: i.e. a blown out tire, a tank fire, subsequent structural issues, and at least two engines (of 4) not running properly.
The official accident report summarizes the causes pretty well (and is worth a read)

The accident was due to the following causes:
• High-speed passage of
  a tyre over a part lost by an aircraft that had taken off five minutes
  earlier and the destruction of the tyre.
• The ripping out of a large
  piece of tank in a complex process of transmission of the energy
  produced by the impact of a piece of tyre at another point on the
  tank, this transmission associating deformation of the tank skin and
  the movement of the fuel, with perhaps the contributory effect of
  other more minor shocks and /or a hydrodynamic pressure surge.
• Ignition of the leaking fuel by an electric arc in the landing gear
  bay or through contact with the hot parts of the engine with forward
  propagation of the flame causing a very large fire under the
  aircraft’s wing and severe loss of thrust on engine 2 then engine 1.

None of these are related to the design or construction of the airframe itself. This podcast with one of the pilots also touches upon the accident and is perhaps one of the best primary sources of Concorde info.

The tyres were redesigned before return to service. That at least indirectly indicates that the original design, if not faulty, had at least room for improvement. Concorde also had history of pieces hitting tanks due to fragmented tyres. IMO, also the second bullet is directed to airframe design; I don’t recall similar failure mechanism ever occuring on any other airliner despite huge number of tyre failures through out the decades. Also large wing gives lots of surface for tyre fractures to hit.

@busdriver the tanks' inside skin was also redesigned. Yes an aircraft design during one period can be improve 30 years later.


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What is the most critical data to measure for a predictive maintenance model for a drone?
I'm looking at making a predictive maintenance model for a drone (quadcopter mainly but can include others)
I'm wondering what is the most common causes of failure due to "overflying". (not including crashes etc) and how I would quantitatively measure it.
eg. I've read that one mode of failure is rotor malfunction is one of the most common causes of faults and so I would therefore use a vibration sensor (positioned near the rotor?) to measure it.
Are there other common failure modes? And what data can we collect from a drone that would help mitigate those?
Any help much appreciated!!
Kindest regards
Jonathan

This is far too broad and non-specific to belong here.  Apart from battery service life issues, likely very few "drones" outside of those that are nearly traditional aircraft without a pilot on board are actually "overflown" but rather most damage will occur from "incidents" and handling during transport and servicing.  You'd need to focus on a particular set of components, look at suspected and actually observed failure modes of those.  For those that are comparable to manned aircraft, start with the incumbent standards for those technologies and add concerns about the unique systems.

Predictive Maintenance (PM) typically relies on a triad of vibration, thermal and oil analysis, or any combination thereof. Probably vib and thermal would apply. Cheapest option would be to physically hold the drone while running (if possible) and acquire vib and thermal, using handheld instruments. All-in option would be a hardwired system, permanently installed. With a hardwired system, you'll need a vib and a thermal transducer installed on each power/rotor module. Hope this helps.


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Caravan 208B EX Glide ratio
What is the glide ratio for the new EX Cessna 208B with 8750 amphibian floats?

You would have to ask someone in the engineering dept at Wipline for an actual number info@wipaire.com.
I have enough float time to be willing to stick my neck out and make a somewhat educated guess. I recall from somewhere that the Caravan on wheels with a feathered prop has a really good L/D by single engine airplane standards, somewhere around 12.
Based on personal experience the glide of most seaplanes is pretty brick-like; I would say a good ballpark would be about a 1/3 to 1/2 reduction in L/D from the land plane.  So for a 208 on amphibs I'm guessing it's going to be between 6 and 8.  If you find out hard data from Wipline, let us know the actual number so I can find out how far off I am.
Fortunately, the PT-6 is so reliable the risk of a power off glide from the engine letting you down is pretty tiny.


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ground staff radio controll
Hoping someone can help me in understand who is who when using a aviation radio. eg: "Delta Delta, Tac"
I understand some of them but am still quite unsure as to who is a sierra, whiskey, alpha etc. hoping someone can help a newbie out

Can you quote a specific conversation?  The same phrase can mean different things in different contexts.  For example, "Delta" may refer to a taxiway, an ATIS update, an Airspace or part of a callsign.

You should start by learning about the phonetic alphabet

Delta, ta[ngo], sierra, whiskey, alpha, etc... are all letters in the ICAO phonetic alphabet, which is a system used to speak letters in a way they can be clearly understood over the radio. Just as letters like "D" and "T" have no particular meaning on their own, these letters can be used to mean many different things depending on the context.
The letters could be part of a callsign (to identify an aircraft, e.g. "november four four charlie kilo" is a particular Cessna Citation), taxiways at an airport ("turn right on taxiway hotel" means turn right onto the taxiway marked "h"), to spell out the name of a location when needed to avoid ambiguity, really anything where spelling out one or more letters is required on the radio.
You might want to read up on the basics of how aviation radio communications are conducted to help understand the format of typical communications.


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How does angle of attack vary during climbing flight?
I'm a little confused by the angle of attack of an aircraft during climbing flight. Suppose you have an aircraft in level flight which then rotates to some angle x. Just after rotation, I would assume that the angle of attack is equal to x, but after this I get confused. The aircraft continues to climb at the angle x, but does the angle of attack vary with time spent in climbing flight? Or once the rotation is over does the angle of attack go back to whatever it is for steady level flight?
Similarly, if you have an aircraft travelling at steady level flight with net lift = 0N, which then rotates to some angle x where for an angle of attack x the net lift is 50N. Does the aircraft only experience this extra 50N of lift for a brief moment during/after rotation, and following that the net lift acting on the wings is again 0N?

Welcome to aviation.SE! For your second question about lift in a climb, this question or this one might help.

Angle of attack is the angle between relative wind, a.k.a. flight path, and the reference datum (chord line in the below image, but might be just given relative to longitudinal axis of the aircraft especially since many aircraft have wing twist, so the chord line varies along span).

(figure from How It Flies section 2.4)
Now to you cases

Just after rotation, I would assume that the angle of attack is equal to x, but after this I get confused.

As the pilot pulls on the control column and the elevators deflect up, the aircraft starts to pitch up. As it pitches up, the angle of attack increases. That increases lift, which is proportional to angle of attack (in the non-stalled region).
As the lift increases, the aircraft will start accelerating upwards, which means its flight path angle will increase. The pitch angle still increases at the same rate, but now the flight path angle also does, so their difference—angle of attack—increase will slow down until it stabilises at some value where the flight path angle rate catches up with the pitch rate.
If the pilot then pushes the control column back and neutralizes the elevator deflection, the aircraft will stop pitching up and the angle of attack will decrease again until the flight path rate stops as well.
In fact the angle of attack at which the aircraft will stabilise is proportional to the elevator deflection (for longitudinally stable aircraft), so if the pilot lets the control column return to its trimmed position, the aircraft will assume the original angle of attack again.
I'll refer you to the mentioned How It Flies chapter 2. Angle of Attack Awareness and Angle of Attack Management for further details.

'As the lift increases, the aircraft will start accelerating upwards, which means its flight path angle will increase. This goes against the increase of angle of attack, which stabilises at some value when the flight path angle rate catches up with the pitch rate'. I think this made everything completely clear to me. So the angle of attack will decrease over time after rotation until the AoA is at whatever angle with the flight vector that is required for steady level climb?

@imveryconfused, the pitch still increases at the same rate, but the flight path angle now also increases, so their difference—angle of attack—stops increasing.

Thank you so much - this is really helpful. Just as an example, say an aircraft pitches to 5 degrees instantaneously (obviously not possible on many accounts, but just for the sake of argument!) and then stops, the angle of attack at that instant is 5 degrees and the extra lift generated by the wings pushes the aircraft upwards. This changes the flight path of the aircraft, decreasing the AoA over time, until the flight path and the AoA are at some angle apart where the aircraft is now in a steady climb?

@imveryconfused, yes, basically back at the same AoA as for level flight, because the lift required during steady climb is a tiny bit less than for level flight (compare vertical flight when weight is completely balanced by engine thrust and lift, which is the horizontal component at that point, is zero) (do read the referenced book, especially the chapters 2 and 4; they do very good job of explaining the physics)

That is really helpful - I can't thank you enough!


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why would an aircraft use 3 red flashing lights?
i saw an aircraft taking off from a supposedly disused airfield with 3 flashing red lights. i live close to Woodford Aerodrome and saw it taking off from there with 3 flashing red lights! i was stood outside having a smoke watching the stars on a lovely clear and very cold night at half 12 and there it was climbing above the roof tops. so i'm curious.

Welcome to av.se!  Unfortunately, "3 red flashing lights" is so little to go on, I suspect that your question is likely to not be well received. A red light on the left wingtip (albeit normally steady) plus a red anti-collision beacon top + bottom is a very, very standard setup for vast numbers of aircraft, so getting a meaningful answer to the question as stated is unlikely. If you can see the aircraft in daylight & provide a better description, or ideally a photo, you're much more likely to get a good answer.

I live near the old Woodford aerodrome and have just seen something very similar. An aircraft with only red navigation lights. It was moving NE to SW (right to left for my view) at a constant but not particularly fast speed. I'm a lifelong aircraft fanatic with 4 years in the air cadets & I'm a qualified skydive. Never seen anything without the standard navigation lights & wondered if anyone had any further thoughts.

Is it possible it was something like a drone or other remotely controlled vehicle? The smaller the vehicle, the lower the lighting standards...

Each plane has 2 Anti-Collision Lights Top and bottom.
A plane also has navigation lights where left is red and right is green these face forward. Navigtion lights are always and don't flash it could look like it if somthing small came in front like birds.

The Lockheed L-1011 Tristar had two anti-collision light on top and two on the bottom. I believe this was because the Tristar was designed from the start for autoland in lower visibility minimas than other aircraft at the time and the designers figured in bad weather it would be good to have more lights?

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S-tec 50 with gns 430
S Tec 50 with an gas 430 navigation question
flying  a 172p with a gns430 and an s-tec 50 , my question is to fly a gps track the 50 has to be in just nav mode ? Some Manuel’s say apr should be on also ? ... hdg mode just follows bug (plane has an hsi)

Might be worthwhile asking your question in a way that would pass muster with a 5th grade English teacher: complete sentence with a subject & verb, punctuation in the appropriate places, etc.  Also, read over the question to see if it makes basic sense as stated. This community can probably provide the answer to the question I think you are asking, but getting that answer is a lot more likely if you would take the time to at least make your question legible on first glance.

Read the supplement in the POH that is required for these types of complex navigation systems with unique attributes.  A short, serious answer is that there is no rule, in the same way that televisions use different menus and navigation paradigms for you to select the video source.

The answer is, it depends on if the plane also has a GPSS (GPS Steering) data converter installed between the GNS-430 and the S-TEC. See my question and answer here regarding how GPSS works in this system - that is, feeding GPS nav data to an S-TEC 50 autopilot. I had the same question about the same setup in my Grumman Tiger.
I found the S-TEC 50 to be an excellent autopilot!
What are the differences between a GPS coupled autopilot and a GPSS autopilot?

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What FAA regulations govern a US International Airport name change, such as McCarran International to Harry Reed International?
What FAA regulations govern a US International Airport name change, such as McCarran International to Harry Reed International or Las Vegas International Airport?  Can the citizenry petition the FAA for or against such a change?

I would think the only thing required would be the owner(s)/manager of the airport would simply notify the FAA of the name change in order to update the documents issued by the FAA. If a citizen wants to protest the renaming, I would think they would have to talk to the Aviation Board that is making the name change - that would be local to them, not the FAA.

The owner of the airport determines the name.  If there is a dispute, courts have settled naming rights.
Whether the airport offers customs determines the "International" designation.  Some airports have no international flights, yet have the "International" in their name. They will have customs available, at least part time.
Side story: At one time, using a grass strip a couple of farms over, I asked a neighbor who worked for US Customs if I could fly directly to the grass strip (which did not even have a FAA Airport Identifier assigned) and clear customs there.  He said I could, and had me notify customs inbound, so they would notify him to meet me at the grass strip for inspection.  Doing that made trips from Canada to back home free of the hassles of dealing with a big airport.


text:
Can pilots turn off warning alarms? Re: Aeroperu Flight 603
I just watched the Mayday S1E4 episode concerning Aeroperu Flight 603.  Gut wretching to see the pilots in that situation.  On listening to the recording tape, alarms were blaring constantly, some for maybe as long as 15 minutes straight.  I can only imagine that that constant blaring adds stress and confusion to the cockpit.  So I wanted to ask if pilots have the ability to silence alarms after a certain period of time?

Sometimes they can sometimes they cant, how to do it varies by aircraft but generally alarms can often be silenced by acknowledging they are going off and pressing some kind of button. On my little Piper Archer the alternator under volt it just a light and can't be shut off but if my G430 throws an alarm or warning it can usually be silenced.
On the 737 some alarms cant be silenced and some can

Cockpit aural warnings include the fire bell, take-off configuration
  warning, cabin altitude, landing gear configuration warning,
  mach/airspeed overspeed, stall warning, GPWS and TCAS. External aural
  warnings are: The fire bell in the wheel well and the ground call horn
  in the nose wheel-well for an E & E bay overheat or IRS’s on DC. Only
  certain warnings can be silenced whilst the condition exists.

A lot of aircraft display failures on some kind of annunciator panel or glass cockpit equivalent. These lights typically can not be turned off until the error is addressed (fire suppressed, breaker pulled etc.). Master Caution lights (and audio warnings) can typically be shut off through the use of a Master Caution Reset switch.

Once notified, the pilot may cancel the master caution, but a
  dedicated system or component annunciator light stays illuminated
  until the situation that caused the warning is rectified. Cancelling
  resets the master caution lights to warn of a subsequent fault event
  even before the initial fault is corrected.

The FAA's full advice on warning and caution light design can be found here.
They shed more light on the topic in this AC

Clearing and Recalling Visual Alert Messages. Clearing visual alert messages from the current warning, caution, and advisory display
  allows the flightcrew to remove a potential source of distraction and
  makes it easier for the flightcrew to detect subsequent alerts. a. The
  following guidance should be applied for clearing and recalling or
  storing the visual alert messages:

(1) If a message can be cleared and
  the condition still exists, the system should provide the ability to
  recall any cleared visual alert message that has been acknowledged. 11
  12/13/2010 AC 25.1322-1
(2) Either through a positive indication on the display or through
  normal flightcrew procedures, a means should be provided to identify
  if alert messages are stored (or otherwise not in view). b. The visual
  alert message must be removed from the display when the condition no
  longer exists (§25.1322(a)(3)).

In short, if a message can be cleared you should be able to pull it back up easily and if the problem goes away the alert should clear as well.

Some alarms, like those announced by the Master Warning System like fire bells, can be silenced by pushing the Mater Warning light and you do it as part of the memory procedure to deal with the warning.  Other alarms, like ones for configurations that are wrong for the conditions, can only be silenced by correcting the configuration.  Think gear warning horns or flap overspeed clackers.
I used to complain about the gear warning horn in the CRJs which has a dual tone that sounds almost exactly like a TV station off-the-air test pattern.  It is extremely easy to blend into the background when the stress level is high and you are becoming mentally saturated. Fortunately, the GPWS announcement "Too Low, Gear" comes on as you get close to the ground to hopefully wake you up.  Hopefully.... some years back a Britair CRJ200 crew landed wheels up in spite of the warnings because they were landing flapless and were mentally saturated by the stress of landing at 160kt (and I believe the GPWS callout may have been inhibited; not sure).


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How much fuel does an airliner consume at various stages of operation?
I used to think that almost all of an airliner's fuel consumption was during actual flight; but it seems that even while on the tarmac or at a gate it consumes a non-negligible amount.
So, in general for modern passenger airliners (say, produced over the past 20 years) and without regard to a specific manufacturer or model:
Let 1.0 be the normalized rate of fuel consumption at typical cruising speed. How much fuel is consumed, on average / typically, when...

Loading passengers?
Taxiing?
Waiting on the tarmac for clearance to take off?
Accelerating and taking off?
Climbing?
Descending?
Touching down and breaking?

Again, rough typical figures please. Or - you could give a concrete example which you believe is representative of the general case.

This is a bit to broad, most numbers are published for specific airframes which we are happy to help with if you are curious about a specific aircraft but an A320 varies quite a bit from a 747-8

Besides How much fuel is used for the different phases of the flight of a typical airliner?, you might also be interested in How much fuel does it take to start/land an aircraft, compared to normal flight? and How much fuel does an airliner consume during passenger boarding? and Does the APU consume a lot of fuel compared to a jet engine?


text:
"Gross" and "net" planned runway length for the Haifa airport
My city's mayor was just boasting on how she'd gotten an approval for an airport runway of length "2100 m gross, 1900 m net length", and that this would be enough to connect the city - Haifa - to hubs all across Europe.
I'm not sure what she meant exactly, but I looked up some aircraft runway requirements, and found this, with no distinction between "gross" and "net" length. Now, some of the Boeing 737 models can fit the "net" length she mentioned, and so can Airbus A319's - but A320s or A321s fall right between the "net" and "gross" lengths.
So, my question is:

Is there such a thing as "gross" vs "net" runway length? If so, what counts into the gross but not the net? Clear space between the tarmac and the perimeter fence maybe?
Was the mayor making an empty boast or can the information about that runway be interpreted so that what she said is correct?

According to Wikipedia, Haifa Airport's runway is currently 1318m long, with plans to extend it by 316m to 1634m. None of those numbers match your question.
The terms "gross" and "net" aren't used in this context, but we do talk about "total" and "available" (or "usable") length, which could just be a translation issue. Runways often have a "displaced threshold", which means planes aren't allowed to land at the beginning of the pavement but rather starting some distance beyond. In the case of Haifa, the threshold for runway 16 is displaced by 50m (leaving only 1268m available) and runway 34 by 119m (leaving only 1199m available). The full length is available for takeoffs. This is extremely short and will indeed severely limit what planes can land there.
The plan is to extend the runway by putting the road at one end into a tunnel. Not only will this increase the total length of the pavement, but it will reduce (or maybe even eliminate) the need for displacement, further increasing how much of the pavement is available. This is still fairly short and limiting by commercial airport standards, but it is still a significant improvement and perhaps enough to make flights to Europe viable for airlines.

Wikipedia might not be up-to-date on this - especially in English.

@einpoklum I checked a translation of the Hebrew version, and that listed past plans to increase to 2000m and 2400m, but both were rejected by national authorities and the 1600m plan is the one currently on the books.

There was this more recent video interview where the mayor said what I quoted her as saying. But who knows.

Gross and net are not aviation terms for runways. Many runways have extra space on either end to be used as stopways, giving extra stopping distance in case of an overrun.

I'm going to hazard a guess and say that the gross length is the total paved area of the runway and the net length is between the thresholds that is usable for takeoffs and landings.

and the aircraft requirements are of "net" runway, I assume?

Normally yes @einpoklum

Wouldn't 'net' be between the threshold for that direction and the far end of the runway? (And presumably the whole length for takeoff).

That's exactly what I'm saying @Zeus, net is the distance between the thresholds.


text:
How come PSA airlines got the same IATA code as Comair?
PSA Airlines has the same IATA 2-letter code, "OH", as the now-defunct carrier Comair. Yet - the two companies are not related.
How is it, that IATA reassigned the same code to an unrelated carrier rather than assigning a new code? Are there any other cases of this happening?

I would guess that since Comair is defunct, there is no chance of conflict in paperwork, routing, or ATC communications when using "OH" to refer to PSA, so there's no concern about reusing the IATA code.

@FreeMan: That just means it is feasible to do this, it doesn't mean it's a good idea... why have codes if they're not unique? It's not like IATA is out of two-char codes for airlines.

The Wiki page gives a straight-foward explanation of how, when, and why codes are reused. https://en.wikipedia.org/wiki/Airline_codes


text:
Why does the Aurora D8 have vents on the bottom of its fuselage?
The Aurora D8 is a concept of an experimental aircraft (not an actual aircraft for now), described in this site. It's discussed in this question here on Aviation.SX.
I was watching the embedded video on the website I linked to, and it seems to show a couple of (intake?) vents on the bottom of the fuselage. You can even see this in the freeze-frame before playing the video.
What could these be used for? Do they suck in air for use in the engine? In the cabin? Elsewhere?

Are your referring to the two round, donut-shaped dark areas on the bottom of the fuselage between the wings? If so, rather than vents, those would presumably be the landing gear in the retracted position. See the wheel well of the B737 for a similar configuration.

@JWalters: Indeed, I accepted that answer.

If you're talking about the dark spots here...

...then those are the tires of the main landing gear. This is the same approach used by the Boeing 737 — as discussed in another question here.
By skipping main landing gear bay doors, the aircraft's total weight is reduced. An aerodynamicist could provide a more confident answer, but the impact of the exposed wheels to the airflow would be relatively minor and not impact drag meaningfully.


text:
Can an airline rewrite a flight's origin airport for the day, following an earlier diversion?
Suppose a domestic US civilian carrier regularly flies flight N directly from airport A to airport B, and flies back flight M from B to A.
Now, one day, the aircraft flying N is diverted to airport C, and the flight ends there (it doesn't continue to B).
Is it possible for the airline to have the aircraft fly from C to B and call that flight M? Even though that's not the route of flight M?
(By "possible" I mean "known to happen", "conceivable" rather than whether it's legal under FAA regulations, although that's interesting too.)

In my experience, flight N will be amended to A-C, and a new flight (probably also called N) will be added C-B, and then flight M will operate B-A as usual.

@StephenS: That's a "standard" diversion, and it makes sense, as no passengers of N would be called upon to board at an airport they didn't expect.  The question is can flight M somehow blink into existence even though nobody was expecting it.

There’s nothing stopping them from doing it that way if they wanted to; it would just be confusing to the passengers and gate agents since the flight number wouldn’t match the tickets when they reboarded at C.

@StephenS: ... but you don't know of this ever happening?

DV for three things:  1.)  Logical fallacy in the scenario - If the flight lands at C and ends there, not continuing to B, then it does not fly from C to B and there is no event to "rewrite".  (It either flies C - B or it doesn't, pick one!)   2.)  The term "rewrite" isn't defined and can be interpreted very broadly.  I assume you mean assign a different flight number, but if that is what you mean why not simply say so?  3.)  Asking if something is possible or conceivable is generally way too broad.  (Is there a reason why renumbering a flight might be inconceivable or impossible to you?)

...and if your intent is to distinguish between a later continuation of the first revenue flight with the intent to get passengers to point B versus a later deadhead non-revenue flight, then the question ought to say that.  Don't make us guess at what you are looking for...

@MichaelHall: I believe you misunderstood my question. Aircraft != Flight. Flight N ends at C, then flight M starts at C. The rewriting is of the origin point for flight M.

@einpoklum, If A-B is named as event N, and B-A is named as event M, then C-B does not meet the definition of either one, and therefore should be assigned a new discrete event name in order to avoid confusion.  I think I understand the basic question, I'm just baffled at how and why it's being asked.

Perhaps you could provide more insight into your thinking by explaining the significance of the exclamation point in "Aircraft !"?  Is that a typo, or a programing language symbol that gives the physical object "aircraft" some logic property that is escaping me?  Because I would disagree that Aircraft=Flight.  One is clearly a noun, but the other could be noun as the object of a sentence, but otherwise is a variation of the verb "fly".  So, an event such as a flight is clearly different than an aircraft, although the latter is obviously required by the former...

Aircraft + Event = Flight.  I don't see this being productive or providing useful insight, but I get frustrated at miscommunication, and this superficially simple question has become a burr under my saddle as I try to understand the root of it...

aircraft + event != flight, AFAIAC: A flight (again AFAIAC) is a sequence of scheduled flight legs, with a flight legs being an aircraft taking passengers between one airport and another. And that sequence of scheduled legs is assigned a number.

Do you not think it might be useful to define AFAIAC?  Because this is just more abstraction as I see it...  (in case you thought that somehow you were answering my question)

No.  They've sold tickets for people to get from A to B. They've not sold tickets to anybody looking to get from C to B.
The aircraft would be ferried into position empty, then they'd operate the schedule that has been advertised & sold.
The scenario as presented doesn't really work, though... you don't get to just strand your passengers in C who bought tickets to A & tell them "sorry, good luck." Either you bus them the rest of the way, or you use AN aircraft and A crew to get them where they need to be. Whether it's the same aircraft and/or the same crew as originally planned depends on various things, but as a matter of flight numbers, you fly what you've been selling tickets for (as much of that schedule as you can) and you ferry planes & crews into position when you have to.
But rewriting things so that "flight #X now starts in C instead of A, today" doesn't happen.

A bus might be part of the scenario, but it's not an aircraft flying those people, so it wasn't what I care about. Naturally. the airline needs to do something for the passengers. Maybe they'd go on another flight, with another number, from C to B later on.

Also - when this aircraft would be ferried, that's not considered a flown leg of a flight of that carrier, right? Just airline operational logistics, so to speak?

If a flight going to LGA (New York LaGuardia) diverted to JFK (New York Kennedy), and the weather would remain too low to get in to LGA for several hours, they could use a bus to get the pax to LGA. If the flight diverted to Boston, probably not.

Re the 2nd question ("also"): a ferry flight has its own flight number, typically outside the normal range of flight numbers that are on the published schedule. And, due to the nature of it, no tickets are sold for those. Beyond that, what it is "considered" would depend on who is doing the considering.  But it isn't a passenger-carrying flight, if that helps.

It does help, because I'm looking at the US DOT's BTS on-time flight performance data, and (AFAICT) that only has passenger flights.

Ferry flights don't have a published departure/arrival time to compare their actual performance against, so yeah, the DOT stats wouldn't consider them. Ditto with maintenance check flights (FCFs), training flights, aircraft deliveries, etc.  As a ticket-buying pax, I wouldn't care how marvelously on-time any of those flights were, anyway, just how well the airline meets its published schedule.

@einpoklum, so by "write" you meant write data to a file?

@MichaelHall: No, I meant rewrite-everywhere, including in public announcements at the terminal, on websites, in its own logs, etc.

@einpoklum, Including flight plan with ATC?  Because the answer varies by context, and per my critique above you need to define what you are looking for specifically.

@MichaelHall: I want to say "no", but that's because I'm not interested in ATC flight plans. Just whatever's facing the public.

Well, sort of. The continuation flight might use the original number, but the original flight must keep it unless it is cancelled.
Lets say flight 621 diverts on 25th and you send a plane to continue it, which will only get there on 26th. If flight 621 normally operates on 26th from A to B, it will have to keep the number 621, because that's what there are tickets for. The continuation flight from C can, however, also use number 621. It is departing different airport, and if it will still arrive at B well before the one scheduled for 26th, that's not a problem. See also Can an airline schedule two same-number flights to leave the same airport on the same day?. And if flight 621 isn't scheduled on 26th, well, then the number is free anyway.
That isn't rewriting the origin. It is a different flight with the same number in either case. And more likely it will get some disambiguation character, so it will be flight 621A or 2621 or such.
It is also unlikely for a domestic flight in the USA to be continued on the next day at all. There is enough air traffic that it's unlikely you wouldn't be able to get the passengers on other flights within a day if you can't get or charter a replacement aircraft for a day.
For an international flight there are such cases though. If you fly from South Africa and have to divert to Ascension Island, well, there is no other option than to send a replacement plane (that will also bring mechanics and spare parts to fix the first one) and it is likely to take a day to get it there. And it could even happen that the flight on 25th that diverted was full, but the flight on 26th is half empty and the smaller airline does not have another plane available, so it cancels the flight on 26th, rebooks the passengers from 26th on other flights and sends the plane to pick the stranded passengers from 25th, operating under the original flight number. And then they sort of rewrote the flight's origin, though it's really still rather a different flight with the same number.

My question is about flights all on the same day...

@einpoklum, that would simply be continuation of the flight with a new aircraft, and there is absolutely no problem with it. It wouldn't be rewriting of origin though, just adding a stop.

"Simply be continuation of the flight" - that would make sense; but that's not what I asked about. I asked about when it is not a continuation of the flight, but supposedly a different flight, with a different number.

@einpoklum, If it is a completely different flight, with a flight different number, and takes off from a different airport, what possible reason might there be for "writing" some alternate "origin" on the basis of a prior leg that was never completed? What would be the rationale for doing so? I'm just having a hard time understanding what your confusion is all about...

@MichaelHall note however that it is quite normal for one flight number to be used to a number of successive flight legs (leg = take-off to landing), including sometimes flown by different aircraft. So in that sense landing (due to emergency) and a replacement aircraft continuing with the same flight number is no different from a multi-leg flight.

@Jan Hudec, I understand that, but the OP specified that the second leg was NOT a continuation.  (per their response to your earlier comment directly above...)

@einpoklum, if it is to pick the passengers now stranded at C, it's a continuation. If it isn't, there is no reason for the airline to make that flight, because they didn't sell any tickets from C.

Now, one day, the aircraft flying N is diverted to airport C, and the
flight ends there (it doesn't continue to B).  Is it possible for the
airline to have the aircraft fly from C to B and call that flight M?

No, this is not possible.  There is a flaw in the logic being presented.
There are two mutually exclusive scenarios being described here:  If the aircraft flight ends at C and does NOT continue to B, then the event has terminated.  There is no further flight to call “M”.  The second leg doesn't exist, therefore there is no event to rename.
If the flight DOES continue on to B, then the flight could not have ended there.  It is simply a continuation of the earlier flight.  (You can call it M, or Q, or…)  Any presumption that the flight ended at C is incorrect.

The question is whether this happens, with airlines calling it M.

Whether what happens?  That a flight will be diverted for some reason, and then either cancel or continue?  These things happen regularly...


text:
Which pressure mode of operation has the most stress on aircraft frame
So I am want to know which mode of pressurization has the most demand on the airframe
Isobaric mode
constant - differential mode
unpressurized
I hope to get an answer because I have an exam and need to know
Thank you very much

So what is your understanding on each mode? What is your answer? We can help you but we cannot study for your exam.

Isobaric mode causes the most stress if you keep the cabin pressure and climb higher and higher. (Because the delta pressure and thus the forces become higher and higher)
That's why at high altitudes the isobaric mode is no longer used and the cabin pressurization switches to constant differential pressure instead, which limits the maximum stress.
And unpressurized, well that is not really stressing the hull at all


text:
What is the function of this fixed protrusion on the tail?

(wikimedia.org)
Above you can see a small fixed (?) part on the Embraer 190, just above the KLM logo. It is on both sides of the tail. What is the function of this part?

That is almost certainly a navigation antenna.
From the E190 AOM (Airplane Operations Manual):

You can see the VOR2/LOC2 antenna rather more clearly in this photo:

(The VOR1/LOC1 and VOR3 antennae are embedded within the tailfin.)
Similar nav antennae are used on many smaller aircraft such as (more modern) light aircraft, utility aircraft, business jets and some regional jets.


text:
Disadvantages of using thrust vectoring only in an aircraft with variable rotation nacelles such as the X-19
Take a quad tilt rotor aircraft such as the curtiss-wright X-19 or even a bi-tilt aircraft such as the V-22.
What would be the advantages or disadvantages of using thrust vectoring only for control of roll, pitch and yaw assuming for a moment that there is no added mechanical complexity in individually tilting each nacelle a variable rotation and assuming each nacelle can tilt 180 degrees from full vertical producing downward thrust (lift) to reverse vertical, essentially sending the aircraft downwards.
In theory, the front two nacelles would control pitch by rotating up or down simultaneously while the back two nacelles would control roll by each nacelle tilting oppositely. Combined all nacelles would be capably of controlling yaw or by changing the thrust being generated on each side of the aircraft, a yaw moment could be generated.
of course there are clear issues in the form of Cost, mechanical complexity, control of the aircraft in an engine out scenario, gyroscopic moments and control generally but purely from a flight mechanics perspective, what are the advantages or disadvantages of removing ailerons and using thrust vectoring to control the flight of such an aircraft.
Currently, it is my belief is it would allow the use of highly complex airfoil geometries that would increase the efficiency of the aircraft in flight as airfoils would no longer be necessary and perhaps increase maneuverability of what i would imagine to be large aircraft but there is no drawbacks other than those previously mentioned however, would thrust vectoring produce less turning moments than ailerons?
I look forward to any and all replies, thank you.

There is one disadvantage: it makes control dependent on engines running.
This disadvantage effectively precludes using it on any aircraft carrying people. Usual requirement for a critical system, which controls are, is that the probability of fatal failure must be estimated to be less than $10^{-9}$ per hour of operation. There are simply no propulsion systems that would be as reliable.
Turbine engines themselves have, IIRC, risk of failure on order of $10^{-4}$, so for independent failures you can get below $10^{-9}$ with double redundancy, but common causes—which means mainly various problems with fuel—are included as well and the risk is not low enough. And even triple redundancy is a lot.

It is my belief is it would allow the use of highly complex airfoil geometries that would increase the efficiency of the aircraft.

The best airfoil is one that adaptively changes shape to meet current requirements (read: flaps or flaperons that run the entire length of the wing).

What would be the advantages of using thrust vectoring only for control of roll, pitch and yaw?

That's how the V-22 works. During horizontal short field takeoffs, the engines are angled forward and upward and the flaps are fully deflected to generate maximum lift. Pitch and roll control are provided by thrust vectoring and differential thrust (the V-22 has conventional swashplates). Below is an image of a V-22 during takeoff. (source)

The advantages: Short/Vertical takeoff. More control of the aircraft.
The disadvantages: Everything else.
You mention increased efficiency, but I don't see how that would be possible. The most efficient aircraft are those which generate lift over a large span.
This is because the air you move doesn't need to be accelerated as fast when you are moving large volumes of air at a time. This why gliders for example have such long wing spans.

The problem with gliders however, is they need very long runways to take off and land.
To get the best of both worlds many aircraft use wings which change airfoils depending on what the aircraft is doing. For example deploying flaps during takeoff.
In flight ailerons might cause a bit of parasitic drag, but it's certainly less than 4 rotating propellers pushing in different directions would be.
If you wanted to get even more lift out a standard wing to have shorter takeoff you could use flaperons. Which are basically ailerons that extended the entire wing and are used for control and generating lift.
One aircraft I can think of which merges both worlds together is the V-22. It has 2 rotating propellers which can provide differential thrust, and an airfoil with a solid flap built in to make takeoff as short/efficient as possible.
However outside of the specific military roles this aircraft provides, I don't see much use for it for the general public. I you really need that kind of control helicopters are always available.


text:
Wind vs high altitude cruise
Yesterday I flew back from Tokyo down south against great head wind around 150kt at 34000’, the original flight plan was to cruise at FL240 for a while then climb up, but the captain decided to get up early, which resulted in a longer cruising time.
It became a bit confusing to me in this case,
One, The higher you go the stronger the winds, at the same time the fuel consumption is more efficient, but at what point do you say the wind factors wins over the fuel factors, ex. Take us longer to get to the destination resulting in more fuel burn.
And what are some rule of thumbs to help me develop a decison wether to cruise high or low in terms of fuel saving.
I found a wind altitude trade off in my A321 FCOM, but not too sure if the chart fits my situation, and I’m almost sure the captain didn’t take out the chart to form his decision.
Thank you for your answers on advances. Any input is appreciated.
Best regards,

It is not obvious what you are asking. Maybe you could add some question marks ("?") where they belong to?  ;)

Simply a matter of fuel burn rate per time in air.  Generally you want to go as fast and as high as practically possible against the wind. (Indicated Airspeed - headwind) x Altitude factor = groundspeed (temperature, atmospheric pressure, humidity may be factored in too)
Trip Time hours = Trip Distance miles/Ground Speed miles/hour
Fuel consumption = Trip Time hours x gallons/hour fuel burn rate at given power setting
The pilot may have thought the headwind would be just as bad at FL 240 as at FL 340.
Weather prediction is not perfect, but apparently they did take enough fuel along to make it.
I would give them credit for that.


text:
Is the whole world's airspace covered by ATC?
I'm an enthusiast and have only flown flight/atc simulators (on the VATSIM network). Obviously sometimes the airspace you are flying in is not covered by any ATC (so I have to set my frequency to Unicast). And very often there is only the tower of an airport available. How is it in the real world?

Is the whole world's airspace covered by ATC at all times?
Is any airport covered by all its layers of ATC (Delivery, Ground, Tower, ...) at all times?
How often do pilots use the Unicom frequency because there is no ATC available in current airspace?

These are three mostly separate questions and should be asked that way. Also, you've used two tags about simulators, but your question doesn't mention simulation at all.

Related

The entire world is divided into Flight Information Regions (FIRs), so in theory there is someone responsible for everywhere.  However, those FIRs are then subdivided into different classes of airspace.
Class A/B/C/D/E airspace is "controlled", meaning there should always be some sort of ATC available.  In remote areas, though, ATC may not have radar coverage, so separation would be based only on position reports (plus ADS-B, for participating aircraft).
Class F/G airspace is "uncontrolled"; any ATC service would be advisory only, and around untowered airports, they'll tell you to use CTAF.  Often the reason airspace is uncontrolled in the first place is a lack of radio and/or radar coverage.

I think you need to understand that airspace is divided vertically as well as horizontally. This image should help you picture it (from Australia, where Class B does not exist).

Glass G airspace has no ATC interaction, and in Class E ATC interaction is only needed for IFR flights. When you picture airspace like this, most of the world is not covered by ATC, with the exception being at airliner altitudes where there is almost universal Class A coverage (note, this is not the same as having universal radar coverage).
The majority of the world's airports only have Unicom/CTAF, I'm sure every pilot has flown to one in their training. However only a handful of these airports are used by airlines. And at some towered airports with low traffic, they might not have a distinct delivery frequency, and on quiet days they can go further and combine ground and tower frequencies.

Some towered airports may go even further and only have the tower open at all by request; unless someone files for a flight to it that requires tower services, it operates basically as an uncontrolled airport. One of my nearby airports operates like that, being what is (perhaps informally) knows as class G*, as opposed to class G. You're required to call in entering their airspace and provide position updates, but if there's no answer calling in, you operate as in plain uncontrolled class G with the knowledge that the tower might open at some point while you're in their airspace.


text:
What is the purpose of the black and white stickers on test aircraft?
I want to ask what is the purpose of black and white stickers used on test aircraft.
The following is a picture:

I have seen variations of such stickers. Does anyone know what is reason for their use ?

Related: Checkerboard painted on fuselage of Boeing test aircraft

Oooh, Christmas-wrapped bomb. Very festive!

Those aren't stickers, the plane just has a skin condition.

They appear to be fiducial markers which identify known points on the aircraft, for analysing video footage and performing photogrammetry.
You see similar markers on crash-test dummies used in vehicle impact trials, for instance, and also in motion-capture in the synthetic movie industry (and in orthopaedics).

For the curious, the technical term for these are "fiducial markers". It's the same reason you find black and white stripes and/or checkerboard patterns on some rockets.


text:
How should I build removable wings on a home build?
In the future I would like to build a home built aircraft from scratch, but I would like the aircraft to be able to be hauled by trailer. I would like the wings to be removable but don’t have a definitive answer on how to go about building the wings and how the control cables would connect to the ailerons. I would also like to know how the detachable wings would be attached and kept to the main body of the aircraft securely without falling off. The wings are elliptical that come out straight for about six ribs, then angle up at about 15 degrees.

Quite a few homebuilt aircraft are already designed to be 'trailerable', with either removable or folding wings - google 'trailerable homebuilt aircraft' or 'homebuilt aircraft removable wings'.

Contact your local EAA chapter and ask.

It sounds like you wish to both design and build your first aircraft.  May I suggest that you first home built aircraft should be someone else's design, one that already has the removable wing feature that you want?  That doesn't mean you have to use a kit, but it would mean at least using proven plans.  Then you would not have to learn both aeronautical engineering and how to build an aircraft at the same time.  I hope I am not talking down to you; please correct me if I am off base.

@DanPichelman Hey, you seem to be assuming he's from US... What makes you think so ? AFAIK, EAA is mainly present there, I don't think there are present in many parts of the world.

@kebs - I wasn't assuming the OP's from the US, but I was assuming EAA was global.  Looking at their chapter map it looks like I was mostly wrong - just US & Canada.  That's disappointing.  They make a big fuss about international visitors to Airventure and there are plenty of non-US articles in their magazine.  Thanks for the comment.

Planes on board of aircraft carriers have this: they need to fit all next together in a tight space, so they are made with foldable wings. This photo shows the folding mechanism:
Image source

Both sides of the split end in a full rib plate.
The two ends are connected via two large pins. The upper pin is the fold-up hinge, the lower pin is moved in-out via a hydraulic cylinder.
Aileron control is via a push-pull rod, with a connection bolt right at the wing hinge point, so that the wing part of the linkage can fold up/down.

The vertical black rod keeps the wing up. If one would like to remove the wing completely, only the upper wing pin and the aileron push-pull connection rod would need to be disconnected.

have a look at sailplanes- almost all of them are built to be trailerable, with detachable wings and aileron, trim and flap controls that are detachable too.

Sailplanes are built with removable wings to load on a trailer for transport to another airfield or in case of a land out. Check The Soaring Society of America website for a glider club near you.

Welcome to the site! Will the Soaring Society of America really tell me about glider clubs near me? Remember that about 95% of people in the world live outside the USA.


text:
Is it possible to swap RR trent 900 engines to GP 7200 for existing A380 air frame?
If an A380 was originally equiped with RR trent 900 engines, but decided to switch to GP 7200 for any reason, would this be possible? Has this kind of engine swap (different manufacturer engine swap) been done before?


text:
When did ATA introduce ATA Chapters?
When did ATA introduce the ATA chapters and since when was it used by all manufacturers?
Thanks!

ATA100 was introduced as a publications standard in the late 50s for manuals and was in wide use by the late 60s.  Some manufacturers organized their engineering drawing numbering systems around ATA100 (ex.: flight control systems drawings numbered with a "27" or landing gear with a "32" prefix), but not all.

Thank you for your answer, do you maybe have a source where I can find more information?


text:
Which atmospheric factors that can affect the performance of an aircraft while flying a circuit?
Which atmospheric factors that can affect the performance of an aircraft while flying a circuit?  Apart from the general wind shift.

Welcome to aviation.SE! I'm not sure what you're asking: the factors that affect an aircraft's performance apply in all stages of flight and there's nothing special about being in the circuit. You might want to browse our questions on aircraft performance and perhaps narrow down your question to be more specific. The [tour] may be useful as well, if you aren't familiar with how this site works.

In short, all of them. Environmental factors that affect aircraft performance do so whenever that aircraft is flying, regardless of whether you're flying a circuit, a straight line, or anything in between. The most important environmental factors include:

wind speed
wind direction
air temperature
air density
air pressure

Plus visibility, ceiling, precipitation?


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Why at some airports/airfields you need to fly a non-standard circuit/pattern?
Why at some airports/airfields you need to fly a non-standard circuit/pattern, what are the specific reasons for this and what are the differences between them while flying?

you should give example of airfield where this is the case. I suspect each airfield has its own reason for such pattern.

The specific reasons will likely vary with each individual airport, but the most common reason I've seen is noise abatement.
If the north/south runway is on the west side of town, using right traffic when landing on 18 will keep the planes from flying over the houses.
From the pilot's point of view you fly the circuit making right turns instead of left turns.  It's easy to do and is covered in initial training.

Nearby mountains are also a pretty good reason :-)

@jamesqf - agreed.  Running into them can be noisy

When there are parallel runways, the patterns for each will be away from the parallel runway.  That means that some of the patterns will be RP.


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Why do chunks of aircraft debris float?
In reading about various theories of what happened to flight MH370, there's a lot of discussion about it possibly crashing into the ocean, breaking up, and pieces of the aircraft floating hundreds of miles away.
Is it generally expected that large pieces of an aircraft will float fairly well? E.g. in the linked article, there's a picture of 4 guys carrying what looks like a big chunk of wing. How did that float?
My assumption would have been that that chunk was hollow aluminum fuselage, maybe with some electronics and hydraulics inside, and maybe a portion of a gas tank. I don't get how it would float unless it got lucky and a subsection of gas tank that was empty and did not get pierced during the breakup landed with its inlet/outlet pointing up.
Thanks.

It's important to remember that water is actually very dense. 1 kg/L or 8.3 lb/gal. As a result, lots of things float, Jet-A included.

Parts of MH370 that have been found floating have been sections of flap and other control surfaces and cargo or pax doors and hatches. They are frequently all but sealed sections of the airframe, perhaps with breather holes to allow pressure equalisation but if they are in water with breathers down very little gets in. Airframes are also extensively treated with sealants inside to prevent oxidisation so even a couple of years in seawater does not do them too much harm. Large tanks are not found as they are usually simply sealed parts of the airframe that break up on impact.

Lighter materials such as plastic will naturally float.
Composites can have large sections of honeycomb core with trapped air. Even if these parts are broken, the honeycomb is sealed against both sides of the panel, still trapping air.
Large sections, whether made from composite or metal, will generally be hollow to save weight, and sealed to prevent collecting moisture which could cause corrosion. There may be small drain holes, but they wouldn't be enough to cause significant leaks.
Fuel tanks are sealed but they are also fairly large and contain baffles to allow fuel to flow within the tank. As you would guess, a catastrophic crash would be unlikely to leave a significant portion that doesn't contain holes.
The parts found suspected to be from MH370 all have these qualities.


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Was a point system implemented to train pilots to land on aircraft carriers?
A long while ago a friend of mine told me that early in the history of aircraft carriers, a lot of planes and pilots were lost due to the increased difficulties of landing planes on a moving runway. To address this, he said, a point system was used to train pilots to land more successfully with each action required by the pilot being assigned a number of points (speed, angle of approach, etc).
I have been trying to find information on this for over a year but have been unsuccessful. Have I been misinformed? I'm beginning to think my friend is full of baloney.

"Grading" was the key, as opposed to "points." Thanks for the link.

Not to quibble, (cause this has little to do with the question), but why would there be any more difficulty landing on a moving runway than on a stationary one in a strong wind? In fact, it is probably easier to land on an aircraft carrier in calm conditions than it is to land on a stationary runway in strong and gusty conditions. Naval aviators may correct me, but I would imagine that the thing that makes aircraft carriers difficult to land on is not the fact that it is moving, but the sea conditions, which can cause it to pitch up and down.

Early on in US Naval Aviation, the system began to assign a series of grades for landing performance and set minimum grade requirements to carrier qual and manintain proficiency for naval aviators assigned to carrier based fixed wing squadrons.  The reasoning was to weed out aviators who could not maintain these standards, thus preventing a lot of accidents aboard ship.
A fixed wing carrier pattern and landing has quite a bit in common with that found in terrestrial flying.  However due to the small landing area aboard the ship, the tolerances are considerably tighter and the procedure is more demanding on the aviator.  The Navy found that unless strict standards were adhered to, pilots would begin to lax in their performance and begin to develop bad habits with their flying which could degenerate into dangerous situations.  Therefore all landings aboard ship are now graded by a team of Landing Signal Officers (LSOs).  LSOs are experienced naval aviators who have undergone additional training and experience to become an LSO.  The LSO observes the aviator in the pattern and monitors the pilot’s progress to make sure they’re in the correct position, altitude, airspeed and AoA.  Specific position in the pattern and final approach are graded:

Abeam the platform: the Jet should be abeam the LSO platform on the downwind leg of the pattern, approx 1 mile offset from the port side of the ship, at 600 ft ASL, at a target pattern airspeed, in the landing configuration.
At the 90: the jet should be halfway through the left turn to final approach, perpendicular to the direction the carrier is steaming, about 1 1/2 miles behind the ship, 450 ft AGL, at optimal AoA.
A
Crossing the Wake:  the jet should cross the ship’s wake about a mile behind the ship, 450 ft AGL, at optimal AoA
At the Start: the jet should be lined up in the groove - landing area centerline - and on glideslope - call the ball - about 3/4 mile behind the ship at 450 ft ASL, at optimal AoA.  Major deviations from AoA, lineup and glideslope should be corrected at this point or a go-around should be executed.
In the Middle: in the groove, on glideslope, on AoA.  Any minor deviations should be corrected here. Overshoots and worsening deviations from these targets should require a waveoff.
In close: the jet is 1/4 mile from touchdown, on glideslope, in the groove and very very small corrections being made to maintain these metrics.  Probably the last safe chance for a waveoff, if needed.
At the Ramp:  jet is over the roundout, on glideslope, on groove.  LSO may give the cut signal for the pilot to pull power to idle, if high, but not unsaveable high.
In the Wires: jet touches down (impacts) the deck on the main gear between the #2 and #3 cross deck pendants.  Hook snags the #3 cross deck pendant.  Pilot goes to full power in case of bolter or hook skip and makes ready to go around.
Final Stop: jet comes to a halt in the LA on centerline.  Power to idle.  Disengage the hook from the cross deck pendant.

These positions and metrics are graded and a composite score is released by the LSOs on the platform.  Grades are as follows.

OK Underline:  Superlative pass at the boat conducted with additional complications eg engine failure, barricade landing, etc.  Worth 5 points.
OK “Oh-Kay”: The highest score achievable under standard conditions.  Jet flew pattern and approach with minimal deviations, all promptly corrected for.  Hook snagged the 3-wire.  Good pass worth 4 points.
(OK) “Fair”: A fair pass.  Flying was good but there were a few deviations.  But overall, solid and safe.  Worth 3 points.
OK-Bolter:  a solid and safe pass but hook did not snag a cross deck pendant.  Worth 2.5 points.
No Grade: Too many deviations.  Described by LSOs as “ugly but safe ugly”.  Ironically worth 2 points.
Cut Pass: Unsafe attempt.  Gross deviations outside of the safe margain for flying.  Consider yourself lucky to walk away from this one with only the LSO’s teeth marks in your hinder.  Worth zero points.

A typical review of a pass may read something like.
202 (Jar-Jar): Slightly wide abeam, High at the 90, high and left at the start, slightly high in close, OK.
Squadrons have certain minimum landing GPAs and boarding rates (ratio of traps to total landing passes).  An F-18 squadron might require a GPA of 2.75 with a 60% boarding rate, etc. to remain carrier qualed.
PERSONAL OPINION
I think that grading began as a means of leveraging the competitive nature of the aircrews to motivate better performance.  Again the tolerance between an OK pass and a No Grade are pretty tight compared with landing on terrestrial runways.  Sloppiness can start to creep in unless drilled out.  3-wires start to become 2-wires, then 1-wires, then taxi 1-wires and finally rampstrikes happen and people get killed.  Landing grades are posted in the squadron ready rooms and everyone wants top spot.  If you screw up, everyone’s gonna see it - and it has a serious meaning.

Excellent, thank you so much. It seems the entire reason I was unable to find this myself was because I was looking for "points" rather than "grading." I do agree on the competitive nature of the crews being the most likely reason this works.


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What is this aviation quote?
I remember hearing a quote about aviation that was something along the lines of “asking a pilot why he loves flight is like asking an artist (or a painter?).....”. For the life of me, I cannot remember what this quote is; however, once I saw or heard it, I fell in love with it. I wish I had wrote it down but I didn’t. I could have sworn that I saw this quote on the film “One Six Right” but after going through it multiple times, I have yet to see it written on the screen or heard a person on the film mention it. This question has been bugging me for a couple years and I cannot seem to find any help googling it. Thank you for your help!!

This quote is from Barry Schiff, a retired pilot from TWA and aviation consultant (but this is only the beginning of the story, I invite everybody to read the article on Wikipedia):

Photo stolen from AOPA

Your recollection is accurate! This is indeed in One Six Right.

Landing on 16R at Van Nuys, Youtube
He says that at the beginning (3:06) of the documentary. The video is not available online, but the first sentence of this quote is often taken up, e.g. on page 39 of this Midwest Flyer issue.
The quote in its context:

“Asking someone why they love to fly is almost like asking someone why
  they like Picasso. The beauty is the fact that you can’t really
  describe it, it’s something that you have to behold. Flying takes you
  into another dimension, literally. We see, feel, and experience things
  that people who don’t fly will never know.”
Barry Schiff, Aviation Safety Expert / Pilot (source)


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What's the difference between EFVS and CVS?
What's the difference between EFVS and CVS? Is there any aircraft certified with EFVS?

The FAA recognizes 4 'vision' systems; enhanced vision system (EVS), synthetic vision system (SVS), combined vision system (CVS), and enhanced flight vision system (EFVS).
EVS and EFVS use either passive or active sensors on the aircraft to enhance the crew's vision of the approach. SVS uses a database to generate a synthetic view of the terrain in  front of the aircraft. CVS combines features of EVS or EFVS and SVS.
It's all spelled out in AC 20-167A Airworthiness Approval of Enhanced Vision System, Synthetic Vision System, Combined Vision System, and Enhanced Flight Vision System Equipment

I can’t find a solid confirmation of this, and hopefully someone will fill in the blanks, but Combined Vision Sytem (CVS) appears to be a system that shows both Enhanced Vision System (EVS) and Synthetic Vision System (SVS) data simultaneously on the HUD.
An EVS image is created from the actual environment using sensors on the aircraft. An SVS image is created from a terrain database. CVS systems allow the pilot to see these two simultaneously. There are currently two ways to do this. Honeywell and Rockwell Collins systems approach is to overlay the two. Dassault’s FalconEye system allows the HUD to be split between the two at a line chosen by the pilot.
For more info see Flying Dassault's FalconEye Combined Vision System


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Wing Shape: Long/Wide Span Wings vs Deep Wings
Planes use wings to generate lift. The wider the span of the wing (looking at the plane from the front) the more lift it generates, however, this is at the expense of more drag.
Some planes like the F-22, or hang gliders, however, seem to adopt the strategy of having their wings larger front to back, instead of extending more out to the side. I'd guess that having a deeper wing would also increase lift at the expense drag and weight.
A third way to increase lift at the expense of drag is to increase the angle of attack of the wing, but I am not really interested in that for this question.
What are the advantages and disadvantages of a deeper wing versus a wider wing span?

@fooot thanks, I was not aware of the term aspect ratio

Of course! Welcome to Aviation.SE!


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Why does the P-3 Orion use an engine driven compressor instead of bleed air for pressurization?
In another question, an answer mentions that the P-3 Orion uses a gearbox driven compressor for cabin pressurization, even though the aircraft uses T-56 turbine engines that supply bleed air in other designs.
(How are turboprops and other propeller planes pressurized?)
Brief research suggests that the "EDC" exists, but I can not find any rationale for it.
(http://blueaero.com/wp-content/uploads/2016/11/Heico_P3_EDC_Repair.pdf)
Does using gearbox driven compressors help in some way with the mission, possibly in dealing with the environment? Is it an anachronism/carryover from the L-188 Elektra? Is it not actually gearbox driven, but somehow an exchanger for bleed air?

Bleeding air from compressor reduces air available for combustion and also reduces compression ratio, so it impacts both the engine output and thermal efficiency. You can think of bleed air as the reverse of a supercharger. If engine performance is tight but weight budget is OK, then it make sense to take some power from the output shaft and drive a separate compressor.

@user3528438 In other words, taking bleed air costs more power in lost combustion than the power which is extracted?

Even if it cost no power in lost combustion, you are still stealing power from the HP shaft after all, that alone costs as much power as an external compressor. But in reality lost combustion is many times that.

@user3528438 Makes sense! Thanks for the explanation.

This is only one possible rationale. P-3 may have other reasons that leads to this design. Also some more info here: https://aviation.stackexchange.com/questions/17030/why-is-the-b787-one-of-the-few-aircraft-with-electro-thermal-wing-anti-de-icing

US Navy P-3s commonly operated with 2 or 3 engines shut down to conserve fuel - may have something to do with it - a single active engine would have to provide 4 times as much bleed air as it would with all active, and 2 active engines would need to each provide twice as much.

Retired P-3 Flight Engineer here.
The EDC's were only on the inboard engines, #2 & 3.  The C model and later variants required a fair amount of cooling and the cabin was quite cool for the crew.
Someone mentioned shutting down engines for fuel conservation, while true typically #1 engine was shutdown and if conditions and weight allowed #4 engine could also be loitered.  #1 didn't have a generator or other accessories while #4 only had a generator.
Taking bleed air from the engine robbed horsepower, increased temperature in the combustion chambers and increased fuel consumption which was a major concern.  EDC were reliable and supplied all the air needed for both pressurization and cabin heat or air conditioning.

Welcome to aviation.stackexchange!

The P3 is such a cool aircraft, thanks for sharing the first hand experience!

The T-56 engine, like all turboprops, is much more efficient at converting fuel into rotational energy than compressing air.  It takes approximately 50-100 shaft horsepower to run an EDC, depending on altitude and how cold of a temperature you select. Bleeding a small amount of air off the engine to run engine anti-ice costs you a 9% loss of SHP, which in flight, would be anywhere from 150-250 SHP.  I don't know the exact volume of bleed air you would need to run a pressurization system, but it is definitely more than the engine-anti ice system.  I'm making that assumption base on the size of the ducting.  The anti-ice tubing is much smaller than the EDC tubing, or the main bleed air manifold for that matter.
All in all, I think it's due to efficiency.  The EDC is more efficient for that motor, but is more complicated and introduces more possible malfunctions.  A P-3 requires a LOT of cold air to keep the computers from overheating, more than a C-130 (same motor) for sure.  I'm not sure if the C-130's back in the day also had EDC's, but they use bleed air nowadays.  So the designers went with whatever can move the most air.  I don't have my Orion Service Digests handy, but I bet there's a more thorough answer in there.  I'll check whenever I go back to work.

From memory, the use of air derived directly off an engine compressor assembly was prohibited for the use of air-conditioning (IIRC, it had to do with the possibility of oil leakage/fume contamination from seals within the engine core assembly of the turbine engines) in passenger aircraft - back in the days of the Electra. The Orion simply carried this over from the Electra days. The C130 didn't have these restrictions, as it was designed primarily as a cargo aircraft, not a passenger type aircraft, although plenty of passengers - myself included have flown in both C130 & P3 aircraft.

I think this answer provides a very good reason for this design decision, however you need to provided a source for this statement, otherwise the answer will not be upvoted...


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Do modern aircraft still have PCMCIA?
Do modern aircraft still have PCMCIA for engine monitoring?

I wouldn't be surprised if floppy disk is still in use.

I didn't know they used PCMCIA. I thought they used more specialised hardware.

@ManuH According to this reddit post Airbus, Boeing, and Embraer use (or used) them: "It’s a memory card that goes into the FDIMU (Flight Data Interface and Management Unit) and records various flight parameters, engine performance data, interfaces with the ACMS (Aircraft Condition Monitoring System), ACARS and various other computers on the plane."

My plane uses a micro SD card to download engine performance data.  Other boxes in my plane use a USB stick. The plane is not modern (46 years old) but the avionics are modern and engine monitoring system are new.

Without a clear definition of "modern aircraft", this question is too broad. Many airplanes, even older aircraft that have been retrofitted with newer electronics, won't use PCMCIA, because newer, improved I/O interfaces are available. On the other hand, surely there are some aircraft flying today that are essentially "modern" as compared to the early days of aviation, and which still have PCMCIA interfaces. Please be more specific as to what you consider "modern". (That said, I do doubt that a clean sheet 21st century design would be using PCMCIA.)


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Are all engines fan blades made out of titanium?
I was wondering if all engine fan blades are really made out of titanium.

Of course not all of them. F119 and F135 are the two that does.

Many, but not all. Rolls-Royce has been working on carbon fibre fan blades for a long time, using the material as far back as 1968 on the RR. Conway. They planned to use carbon fibre (Hyfil) for the RB.211 too, but had to switch to titanium when they couldn't get the Hyfil blades to work reliably during bird ingestion tests.
The GE90 uses carbon fibre fan blades, with titanium leading edges.

Others: CFM LEAP and GE9X are composite, the PW1000G is aluminum.


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Do all aircraft carry depleted uranium as counterweights?
I was told that most aircraft had depleted uranium on board as counterweights. I have not seen one myself. Do all current modern aircraft have depleted uranium on board?

Related: What is the reasoning behind using depleted uranium as counterweights in the 747?, most of the counterweights were replaced with tungsten, so no, most aircraft don't use DU weights.

You don’t need anything that exotic; Steel or tungsten will work just fine for that role

Counterweight to what?  I've never noticed any in my 1973 Cessna single engine 4 seater.

I suspect small aircraft just use a big chunk of shaped lead, and not depleted uranium. That would be a nightmare for A/Ps out in the field if any trimming was needed for example.  My parts manual does not appear to say what the parts are made out of.

@CrossRoads: Lead has long been replaced by brass, at least in gliders and motor gliders. When more expensive and denser materials are allowed (= Airbus and Boeing), tungsten is more than twice as heavy per unit of volume and even a notch above uranium.

From my research, it looks like about 0.1% of all aircraft carry depleted uranium counterweights.
The Systematic Radiological Assessment of Exemptions for Source and Byproduct Materials (NUREG-1717), on page 3–260, gives a table showing that 430 domestic United States aircraft were delivered with depleted uranium counterweights, and says that "A reasonable estimate is that 50% of these aircraft still contain DU counterweights." So there are about 200 aircraft in the United States which contain depleted uranium counterweights.
Meanwhile, the FAA's "Air Traffic by the Numbers" publication says that there are over 200,000 aircraft in the United States currently.
So no, very few aircraft use depleted uranium counterweights.

… but those with DU are the very heavy and big beasts, so per mass the fraction is quite a bit higher. Still, it's insignificant.

Is this "all aircraft" in the US, or the world?

@isanae Well, the 0.1% figure is for aircraft in the US, and it seems reasonable to guess that the number is similar for the rest of the world. In particular, the number is certainly not 100%.

That material is dangerous and expensive. It is used only in special situations where the design requirements are stringent and heavily constrained.
For example, the C-5A cargo plane used depleted uranium (DU) to counterweight its main control surfaces.

It's not really expensive, at least at acquisition time. "Tungsten markets for $25 to $45 per pound depending on the form of the metal" "Depleted uranium costs $5 per pound from old stockpiles" and lead is $1 per pound. DU likes to burn so I hope one would use it in oxide form. Being a very heavy metal doing nasty things to biological systems (Uranium Babies are horrendous) and somewhat radioactive, use gloves when handling. Do not inhale. Dispose at specialized municipal waste recycling centers.

@DavidTonhofer, thanks for this, the maintenance techs on the C-5 were "on the clock" when working in proximity to the DU counterweights and had to cycle out after a certain number of hours which I cannot remember...

It's not super radioactive, not that I'd want to handle it all that much.  I'd rather have to worry about a block of DU than, say, a radon build up or dust from uranium ore processing.  I've read that the heavy metal toxicity of uranium will kill you long before the radiation exposure, chemical toxicity estimates put it on a similar LD50 to DDT and MDMA, not all that lethal but still not something to mess with lightly.

Indeed. Consider also this C-5A fact: its main landing gear bogies are cast from beryllium, to save weight. this metal is so severely notch-sensitive for fatigue failure that there are NO radii in the structure less than 12" and the entire assembly is coated with a THICK layer of paint. Why? Because the oxides of beryllium, when inhaled, cause berylosis, a deadly disease. For this reason, maintenance techs on the C-5 are on the clock anytime they are in the main wheel wells, to minimize beryllium exposure via scratches in the paint...

@DavidTonhofer - Formula 1 cars used depleted uranium for ballast until sometime around 2001. It was disallowed not because of the toxicity, but because of cost. By the time teams got the depleted uranium, it cost about  7500 (US dollars) per kilogram. A team supporting 3 cars at around 22 kg of ballast per car would end up spending close to 500,000 (US dollars).

@rcgldr Must be the transport, paperwork, special handling and following of Health&Safety rules (as well as only a few companies willing to do the metalwork). I can't imagine tank armor or antitank ammunition costing that much. (How come Formula 1 regulations can forbid pricey equipment? Do they define a cost envelope for the team?)

No.  For example, recently-manufactured modern paragliders and hang gliders contain no uranium.

It was once my understanding that the FAA took the position that ultralights weren't aircraft, but later someone pointed out to me that this wasn't really true, even though FAR 103 does avoiding using the term "aircraft".  I can't recall more details of the thrust of the argument at the moment but basically it was that ultralights may NOT be considered exempt from regulations pertaining to "aircraft".